Long-term heat aging resistant polyamide compositions

ABSTRACT

Disclosed is a thermoplastic composition including (A) a polyamide resin selected from the group consisting of Group (III) Polyamides including (a) about 20 to about 35 mole percent semiaromatic repeat units derived from monomers selected from one or more of the group consisting of (i) aromatic dicarboxylic acids; and (b) about 65 to about 80 mole percent aliphatic repeat units; (B) one or more polyhydric alcohols having more than two hydroxyl groups and a having a number average molecular weight (M n ) of less than 2000; and (C) 0 to 60 weight percent of one or more reinforcement agents.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of U.S. ProvisionalApplication No. 61/137,345, filed on 30 Jul. 2008 and currently pending.

FIELD OF INVENTION

The present invention relates to the field of polyamides compositionshaving improved long-term high temperature aging characteristics.

BACKGROUND OF INVENTION

High temperature resins based on polyamides possess desirable chemicalresistance, processability and heat resistance. This makes themparticularly well suited for demanding high performance automotive andelectrical/electronics applications. There is a current and generaldesire in the automotive field to have high temperature resistantstructures since temperatures higher than 150° C., even higher than 200°C., are often reached in underhood areas of automobiles. When plasticparts are exposed to such high temperatures for a prolonged period, suchas in automotive under-the-hood applications or inelectrical/electronics applications, the mechanical properties generallytend to decrease due to the thermo-oxidation of the polymer. Thisphenomenon is called heat aging.

In an attempt to improve heat aging characteristics, it has been theconventional practice to add heat stabilizers (also referred asantioxidants) to thermoplastic compositions comprising polyamide resins.Examples of such heat stabilizers include hindered phenol antioxidants,amine antioxidants and phosphorus-based antioxidants. For polyamidecompositions, three types of heat stabilizers are conventionally used toretain the mechanical properties of the composition upon exposure tohigh temperatures. One is the use of phenolic antioxidants optionallycombined with a phosphorus based synergist as previously mentioned, theuse of aromatic amines optionally combined with a phosphorus basedsynergist and the third one is the use of copper salts and derivatives.Phenolic antioxidants are known to improve the mechanical/physicalproperties of the thermoplastic composition up to an aging temperatureof 120° C.

U.S. Pat. No. 5,965,652 discloses a thermally stable polyamide moldingcomposition containing colloidal copper formed in situ. However, thedisclosed compositions exhibit retention of impact strength only for aheat aging at 140° C.

GB patent 839,067 discloses a polyamide composition comprising a coppersalt and a halide of a strong organic base. However, the disclosedcompositions exhibit improved bending heat stability performance onlyfor a heat aging at 170° C.

Existing technologies lead not only to a poor improvement of long-termheat aging resistance, but also the improved heat aging characteristicsare insufficient for more demanding applications involving exposure tohigher temperatures such as for example in automotive under-the-hoodapplications and in electrical/electronics applications.

US 2006/0155034 and US 2008/0146718 patent publications disclosepolyamide compositions comprising a metal powder as thermal stabilizerwith a fibrous reinforcing agent. Disclosed compositions exhibitimproved mechanical properties such as tensile strength and elongationat break upon long-term heat aging at 215° C. However, such metalpowders are not only expensive but they are also highly unstable becausethey are prone to spontaneous combustion.

EP 1041109 discloses a polyamide composition comprising a polyamideresin, a polyhydric alcohol having a melting point of 150 to 280° C.,that has good fluidity and mechanical strength and is useful ininjection welding techniques.

Unfortunately, with the existing technologies, molded articles based onpolyamide compositions either suffer from an unacceptable deteriorationof their mechanical properties upon long-term high temperature exposureor they are very expensive due to the use of high- cost heatstabilizers.

There remains a need for low-cost polyamide compositions that aresuitable for manufacturing articles and that exhibit good mechanicalproperties after long-term high temperature exposure.

SUMMARY OF INVENTION

Disclosed is a thermoplastic composition comprising

A) a polyamide resin comprising on or more polyamides selected from thegroup consisting of Group (III) Polyamides comprising

-   -   (a) about 20 to about 35 mole percent semiaromatic repeat units        derived from monomers selected from one or more of the group        consisting of:        -   (i) aromatic dicarboxylic acids having 8 to 20 carbon atoms            and aliphatic diamines having 4 to 20 carbon atoms; and    -   (b) about 65 to about 80 mole percent aliphatic repeat units        derived from monomers selected from one or more of the group        consisting of:        -   (ii) an aliphatic dicarboxylic acid having 6 to 20 carbon            atoms and said aliphatic diamine having 4 to 20 carbon            atoms;        -   (iii) a lactam and/or aminocarboxylic acid having 4 to 20            carbon atoms;

B) about 0.25 to about 15 weight percent of one or more polyhydricalcohols having more than two hydroxyl groups, the weight percentagebeing based on the total weight of said thermoplastic composition; and

C) 0 to 60 weight percent of one or more reinforcement agents.

DETAILED DESCRIPTION

For the purposes of the description, unless otherwise specified,“high-temperature” means a temperature at or higher than 170° C.,preferably at or higher than 210° C., and most preferably at or higherthan 230° C.

In the present invention, unless otherwise specified, “long-term” refersto an aging period equal or longer than 500 hrs, preferably equal orlonger than 1000 hrs.

As used herein, the term “high heat stability”, as applied to thepolyamide composition disclosed herein or to an article made from thecomposition, refers to the retention of physical properties (forinstance, tensile strength) of 4 mm thick molded test bars consisting ofthe polyamide composition that are exposed to air oven aging (AOA)conditions at a test temperature at 170° C. for a test period of atleast 500 h, in an atmosphere of air, and then tested according to ISO527-2/1A method. The physical properties of the test bars are comparedto that of unexposed controls that have identical composition and shape,and are expressed in terms of “% retention”. In another preferredembodiment the test temperature is at 210° C., the test period is at 500hours and the exposed test bars have a % retention of tensile strengthof at least 70%. Herein “high heat stability” means that said moldedtest bars, on average, meet or exceed a retention for tensile strengthof 50% when exposed at a test temperature at 170° C. for a test periodof at least 500 h. Compositions exhibiting a higher retention ofphysical properties for a given exposure temperature and time periodhave better heat stability.

The terms “at 170° C.” and “at 210° C.” refer to the nominal temperatureof the environment to which the test bars are exposed; with theunderstanding that the actual temperature may vary by ±2° C. from thenominal test temperature.

The term “(meth)acrylate” is meant to include acrylate esters andmethacrylate esters.

The term “blending polyamides” are a group of polyamides that aresuitable for blending with the Group (IV) to Group (VI) Polyamides, asdisclosed hereafter, to form a polyamide blend.

Herein melting points and glass transitions are as determined withdifferential scanning calorimetry (DSC) at a scan rate of 10° C./min inthe first heating scan, wherein the melting point is taken at themaximum of the endothermic peak and the glass transition, if evident, isconsidered the mid- point of the change in enthalpy.

The thermoplastic composition used in the present invention comprises acopolyamide.

Polyamides are condensation products of one or more dicarboxylic acidsand one or more diamines, and/or one or more aminocarboxylic acids,and/or ring-opening polymerization products of one or more cycliclactams. Suitable cyclic lactams are caprolactam and laurolactam.Polyamides may be fully aliphatic or semi-aromatic.

Fully aliphatic polyamides used in the resin composition of the presentinvention are formed from aliphatic and alicyclic monomers such asdiamines, dicarboxylic acids, lactams, aminocarboxylic acids, and theirreactive equivalents. A suitable aminocarboxylic acid is11-aminododecanoic acid. Suitable lactams are caprolactam andlaurolactam. In the context of this invention, the term “fully aliphaticpolyamide” also refers to copolymers derived from two or more suchmonomers and blends of two or more fully aliphatic polyamides. Linear,branched, and cyclic monomers may be used.

Carboxylic acid monomers comprised in the fully aliphatic polyamidesinclude, but are not limited to aliphatic carboxylic acids, such as forexample adipic acid (C6), pimelic acid (C7), suberic acid (C8), azelaicacid (C9), decanedioic acid (C10), dodecanedioic acid (C12),tridecanedioic acid (C13), tetradecanedioic acid (C14), andpentadecanedioic acid (C15). Diamines can be chosen among diamineshaving four or more carbon atoms, including, but not limited totetramethylene diamine, hexamethylene diamine, octamethylene diamine,decamethylene diamine, dodecamethylene diamine, 2-methylpentamethylenediamine, 2-ethyltetramethylene diamine, 2-methyloctamethylenediamine;trimethylhexamethylenediamine, meta-xylylene diamine, and/or mixturesthereof.

The semi-aromatic polyamide is a homopolymer, a copolymer, a terpolymeror more advanced polymers formed from monomers containing aromaticgroups. One or more aromatic carboxylic acids may be terephthalate or amixture of terephthalate with one or more other carboxylic acids, suchas isophthalic acid, phthalic acid, 2-methyl terephthalic acid andnaphthalic acid. In addition, the one or more aromatic carboxylic acidsmay be mixed with one or more aliphatic dicarboxylic acids, as disclosedabove.

Preferred polyamides disclosed herein are homopolymers or copolymerswherein the term copolymer refers to polyamides that have two or moreamide and/or diamide molecular repeat units. The homopolymers andcopolymers are identified by their respective repeat units. Forcopolymers disclosed herein, the repeat units are listed in decreasingorder of mole % repeat units present in the copolymer. The followinglist exemplifies the abbreviations used to identify monomers and repeatunits in the homopolymer and copolymer polyamides (PA):

-   -   HMD hexamethylene diamine (or 6 when used in combination with a        diacid)    -   T Terephthalic acid    -   AA Adipic acid    -   DMD Decamethylenediamine    -   6 ε-Caprolactam    -   DDA Decanedioic acid    -   DDDA Dodecanedioic acid    -   I Isophthalic acid    -   MXD meta-xylylene diamine    -   TMD 1,4-tetramethylene diamine    -   4T polymer repeat unit formed from TMD and T    -   6T polymer repeat unit formed from HMD and T    -   DT polymer repeat unit formed from 2-MPMD and T    -   MXD6 polymer repeat unit formed from MXD and M    -   66 polymer repeat unit formed from HMD and M    -   10T polymer repeat unit formed from DMD and T    -   410 polymer repeat unit formed from TMD and DDA    -   510 polymer repeat unit formed from 1,5-pentanediamine and DDA    -   610 polymer repeat unit formed from HMD and DDA    -   612 polymer repeat unit formed from HMD and DDDA    -   6 polymer repeat unit formed from ε-caprolactam    -   11 polymer repeat unit formed from 11-aminoundecanoic acid    -   12 polymer repeat unit formed from 12-aminododecanoic acid

Note that in the art the term “6” when used alone designates a polymerrepeat unit formed from ε-caprolactam. Alternatively “6” when used incombination with a diacid such as T, for instance 6T, the “6” refers toHMD. In repeat units comprising a diamine and diacid, the diamine isdesignated First. Furthermore, when “6” is used in combination with adiamine, for instance 66, the first “6” refers to the diamine HMD, andthe second “6” refers to adipic acid. Likewise, repeat units derivedfrom other amino acids or lactams are designated as single numbersdesignating the number of carbon atoms.

Polyamides useful as blending polyamides in various embodiments includeGroup (I) Polyamides having a melting point of less than 210° C., andcomprising an aliphatic or semiaromatic polyamide selected from thegroup poly(pentamethylene decanediamide) (PA510), poly(pentamethylenedodecanediamide) (PA512), poly(ε-caprolactam/hexamethylenehexanediamide) (PA6/66), poly(ε-caprolactam/hexamethylene decanediamide)(PA6/610), poly(ε-caprolactam/hexamethylene dodecanediamide) (PA6/612),poly(hexamethylene tridecanediamide) (PA613), poly(hexamethylenepentadecanediamide) (PA615), poly(ε-caprolactam/tetramethyleneterephthalamide) (PA6/4T), poly(ε-caprolactam/hexamethyleneterephthalamide) (PA6/6T), poly(ε-caprolactam/decamethyleneterephthalamide) (PA6/10T), poly(ε-caprolactam/dodecamethyleneterephthalamide) (PA6/12T), poly(hexamethylenedecanediamide/hexamethylene terephthalamide) (PA610/6T),poly(hexamethylene dodecanediamide/hexamethylene terephthalamide)(PA612/6T), poly(hexamethylene tetradecanediamide/hexamethyleneterephthalamide) (PA614/6T), poly(ε-caprolactam/hexamethyleneisophthalamide/hexamethylene terephthalamide) (PA6/61/6T),poly(ε-caprolactam/hexamethylene hexanediamide/hexamethylenedecanediamide) (PA6/66/610), poly(ε-caprolactam/hexamethylenehexanediamide/hexamethylene dodecanediamide) (PA6/66/612),poly(ε-caprolactam/hexamethylene hexanediamide/hexamethylenedecanediamide/hexamethylene dodecanediamide) (PA6/66/610/612),poly(2-methylpentamethylene hexanediamide/hexamethylenehexanediamide/hexamethylene terephthamide) (PA D61661 /6T),poly(2-methylpentamethylene hexanediamide/hexamethylene hexanediamide/)(PA D6/66), poly(decamethylene decanediamide) (PA1010),poly(decamethylene dodecanediamide) (PA1012), poly(decamethylenedecanediamide/decamethylene terephthalamide) (PA1010/10T)poly(decamethylene decanediamide/dodecamethylenedecanediamide/decamethylene terephthalamide/dodecamethyleneterephthalamide (PA1010/1210/10T/12T), poly(11-aminoundecanamide)(PA11), poly(11-aminoundecanamide/tetramethylene terephthalamide)(PA11/4T), poly(11-aminoundecanamide/hexamethylene terephthalamide)(PA11/6T), poly(11-aminoundecanamide/decamethylene terephthalamide)(PA11/10T), poly(11-aminoundecanamide/dodecamethylene terephthalamide)(PA11/12T), poly(12-aminododecanamide) (PA12),poly(12-aminododecanamide/tetramethylene terephthalamide) (PA12/4T),poly(12-aminnododecanamide/hexamethylene terephthalamide) (PA12/6T),poly(12-aminododecanamide/decamethylene terephthalamide) (PA12/10T)poly(dodecamethylene dodecanediamide) (PA1212), and poly(dodecamethylenedodecanediamide/dodecamethylene dodecanediamide/dodecamethyleneterephthalamide)) (PA1212/12T).

Group (I) Polyamides may have semiaromatic repeat units to the extentthat the melting point is less than 210° C. and generally thesemiaromatic polyamides of the group have less than 40 mol percentsemiaromatic repeat units. Semiaromatic repeat units are defined asthose derived from monomers selected from one or more of the groupconsisting of: aromatic dicarboxylic acids having 8 to 20 carbon atomsand aliphatic diamines having 4 to 20 carbon atoms.

Other polyamides useful as blending polyamide compositions in variousembodiments include Group (II) Polyamides having a melting point of atleast 210° C., and comprising an aliphatic polyamide selected from thegroup consisting of poly(tetramethylene hexanediamide) (PA46),poly(ε-caprolactam) (PA 6), poly(hexamethylenehexanediamide/(ε-caprolactam/) (PA 66/6) poly(hexamethylenehexanediamide) (PA 66), poly(hexamethylene hexanediamide/hexamethylenedecanediamide) (PA66/610), poly(hexamethylenehexanediamide/hexamethylene dodecanediamide) (PA66/612),poly(hexamethylene hexanediamide/decamethylene decanediamide)(PA66/1010), poly(hexamethylene decanediamide) (PA610),poly(hexamethylene dodecanediamide) (PA612), poly(hexamethylenetetradecanediamide) (PA614), poly(hexamethylene hexadecanediamide)(PA616), and poly(tetramethylene hexanediamide/2-methylpentamethylenehexanediamide) (PA46/D6)

Preferred polyamides useful in the invention are Group (III) Polyamidescomprising

-   -   (a) about 20 to about 35 mole percent semiaromatic repeat units        derived from monomers selected from one or more of the group        consisting of:        -   i) aromatic dicarboxylic acids having 8 to 20 carbon atoms            and aliphatic diamines having 4 to 20 carbon atoms; and    -   (b) about 65 to about 80 mole percent aliphatic repeat units        derived from monomers selected from one or more of the group        consisting of:        -   ii) an aliphatic dicarboxylic acid having 6 to 20 carbon            atoms and said aliphatic diamine having 4 to 20 carbon            atoms; and        -   iii) a lactam and/or aminocarboxylic acid having 4 to 20            carbon atoms.

Within the Group (III) Polyamides, preferred are polyamides that have atleast about 60 meq/Kg of amine ends, and preferably at least 70 meq/Kgamine ends. Amine ends may be determined by titrating a 2 percentsolution of polyamide in a phenol/methanol/water mixture (50:25:25 byvolume) with 0.1 N hydrochloric acid. The end point may be determinedpotentiometrically or conductometrically (See Kohan, M. I. Ed. NylonPlastics Handbook, Hanser: Munich, 1995; p. 79 and Waltz, J. E. andTaylor, G. B., Anal. Chem. 1947 19, 448-50).

Other preferred polyamides of Group (III) Polyamides have a meltingpoint of at lest 210° C., and preferably at least 260° C., as determinedwith differential scanning calorimetry at 10° C./min.

Other preferred polyamides of Group (III) Polyamides are wherein saidsemiaromatic repeat unit is derived from terephthalic acid; morepreferably, additionally wherein said aliphatic repeat unit is derivedfrom adipic acid, and more preferably, additionally wherein saidaliphatic diamine is 1,4-butane diamine or 1,6-hexanediamine.

In one embodiment the polyamide resin comprises a Group (III) Polyamidehaving a melting point of at least 210° C., and is selected from thegroup consisting of poly(tetramethylene hexanediamide/tetramethyleneterephthalamide) (PA46/4T), poly(tetramethylenehexanediamide/hexamethylene terephthalamide) (PA46/6T),poly(tetramethylene hexanediamide/2-methylpentamethylenehexanediamide/decamethylene terephthalamide) PA46/D6/10T),poly(hexamethylene hexanediamide/hexamethylene terephthalamide) (PA66/6T), poly(hexamethylene hexanediamide/hexamethyleneisophthalamide/hexamethylene terephthalamide PA66/61/6T, andpoly(hexamethylene hexanediamide/2-methylpentamethylenehexanediamide/hexamethylene terephthalamide (PA66/D6/6T). A mostpreferred polyamide is PA 66/6T.

The polyamides of the present invention may be prepared by any meansknown to those skilled in the art, such as in a batch process using, forexample, an autoclave or using a continuous process. See, for example,Kohan, M. I. Ed. Nylon Plastics Handbook, Hanser: Munich, 1995; pp.13-32. Additives such as lubricants, antifoaming agents, and end-cappingagents may be added to the polymerization mixture. The concentration ofamine ends can be controlled in the preparation of the polyamide byadjusting the pH to control reaction stoichiometry; and controlling theamount of diamine lost in the polymerization process; as a result ofremoval of water from the polymerization reactor. Amine ends may also beadjusted by addition of endcapping agents as is well known in the art. Acommon endcapping agent is acetic acid.

The thermoplastic composition may additionally comprise

-   -   (D) 0.1 to 30 weight percent, and preferably 0.1 to 10 weight        percent, of one or more blending polyamides selected from the        group consisting of Group (I) Polyamides having a melting point        of less than 210° C., as disclosed above and Group (II)        Polyamide having a melting point of at least 210° C., as        disclosed above.

In another embodiment the blending polyamide is selected from Group (I)Polyamides. In another embodiment the blending polyamide is selectedfrom Group (II) Polyamides. In another embodiment preferred blendingpolyamides are selected from poly(ε-caprolactam) (PA 6) andpoly(hexamethylene hexanediamide) (PA 66). The blending polyamides, whenpresent in relatively small weight fractions, in the thermoplasticcomposition provides unexpected and surprising improvements in long-termheat stability, as compared to similar compositions wherein the blendingpolyamide is not present.

The thermoplastic composition comprises 0.25 to 15 weight percent of oneor more polyhydric alcohols having more than two hydroxyl groups and ahaving a number average molecular weight (M_(n)) of less than 2000 asdetermined with gel permeation chromatography (GPC).

Polyhydric alcohols may be selected from aliphatic hydroxylic compoundscontaining more than two hydroxyl groups, aliphatic-cycloaliphaticcompounds containing more than two hydroxyl groups, cycloaliphaticcompounds containing more than two hydroxyl groups, aromatic andsaccharides.

An aliphatic chain in the polyhydric alcohol can include not only carbonatoms but also one or more hetero atoms which may be selected, forexample, from nitrogen, oxygen and sulphur atoms. A cycloaliphatic ringpresent in the polyhydric alcohol can be monocyclic or part of abicyclic or polycyclic ring system and may be carbocyclic orheterocyclic. A heterocyclic ring present in the polyhydric alcohol canbe monocyclic or part of a bicyclic or polycyclic ring system and mayinclude one or more hetero atoms which may be selected, for example,from nitrogen, oxygen and sulphur atoms. The one or more polyhydricalcohols may contain one or more substituents, such as ether, carboxylicacid, carboxylic acid amide or carboxylic acid ester groups.

Examples of polyhydric alcohol containing more than two hydroxyl groupsinclude, without limitation, triols, such as glycerol,trimethylolpropane, 2,3-di-(2′-hydroxyethyl)-cyclohexan-1-ol,hexane-1,2,6-triol, 1,1,1-tris-(hydroxymethyl)ethane,3-(2′-hydroxyethoxy)-propane-1,2-diol,3-(2′-hydroxypropoxy)-propane-1,2-diol,2-(2′-hydroxyethoxy)-hexane-1,2-diol,6-(2′-hydroxypropoxy)-hexane-1,2-diol,1,1,1-tris-[(2′-hydroxyethoxy)-methyl]-ethane,1,1,1-tris-[(2′-hydroxypropoxy)-methyl]-propane, 1,1,1-tris-(4′-hydroxyphenyl)-ethane, 1,1,1-tris-(hydroxyphenyl)-propane,1,1,3-tris-(dihydroxy-3-methylphenyl)-propane,1,1,4-tris-(dihydroxyphenyl)-butane,1,1,5-tris-(hydroxyphenyl)-3-methylpentane, di-trimethylopropane,trimethylolpropane ethoxylates, or trimethylolpropane propoxylates;polyols such as pentaerythritol, dipentaerythritol, andtripentaerythritol; and saccharides, such as cyclodextrin, D-mannose,glucose, galactose, sucrose, fructose, xylose, arabinose, D-mannitol,D-sorbitol, D-or L-arabitol, xylitol, iditol, talitol, allitol,altritol, guilitol, erythritol, threitol, and D-gulonic-y-lactone; andthe like.

Preferred polyhydric alcohols include those having a pair of hydroxylgroups which are attached to respective carbon atoms which are separatedone from another by at least one atom. Especially preferred polyhydricalcohols are those in which a pair of hydroxyl groups is attached torespective carbon atoms which are separated one from another by a singlecarbon atom.

Preferably, the polyhydric alcohol used in the thermoplastic compositionis pentaerythritol, dipentaerythritol, tripentaerythritol,di-trimethylolpropane, D-mannitol, D-sorbitol and xylitol. Morepreferably, the polyhydric alcohol used is dipentaerythritol and/ortripentaerythritol. A most preferred polyhydric alcohol isdipentaerythritol.

In various embodiments the content of said polyhydric alcohol in thethermoplastic composition is 0.25-15 weight percent, preferably 0.5-8weight percent, more preferably 1-5 weight percent, most preferably 2-5weight percent, based on the total weight of said thermoplasticcomposition.

The thermoplastic composition may include 0 to 60 weight percent of oneor more reinforcement agents. In one embodiment the thermoplasticcomposition includes about 10 to 60 weight percent of one or morereinforcement agents.

In another embodiment the composition includes less than 10 weightpercent of one or more reinforcement agents, preferably less than 1weight percent, and most preferably 0 weight percent.

The reinforcement agent may be any filler, but is preferably selectedfrom the group consisting calcium carbonate, glass fibers with circularand noncircular cross-section, glass flakes, glass beads, carbon fibers,talc, mica, wollastonite, calcined clay, kaolin, diatomite, magnesiumsulfate, magnesium silicate, barium sulfate, titanium dioxide, sodiumaluminum carbonate, barium ferrite, potassium titanate and mixturesthereof.

Glass fibers with noncircular cross-section refer to glass fiber havinga cross section having a major axis lying perpendicular to alongitudinal direction of the glass fiber and corresponding to thelongest linear distance in the cross section. The non-circular crosssection has a minor axis corresponding to the longest linear distance inthe cross section in a direction perpendicular to the major axis. Thenon-circular cross section of the fiber may have a variety of shapesincluding a cocoon-type (figure-eight) shape, a rectangular shape; anelliptical shape; a roughly triangular shape; a polygonal shape; and anoblong shape. As will be understood by those skilled in the art, thecross section may have other shapes. The ratio of the length of themajor axis to that of the minor access is preferably between about 1.5:1and about 6:1. The ratio is more preferably between about 2:1 and 5:1and yet more preferably between about 3:1 to about 4:1. Suitable glassfiber are disclosed in EP 0 190 001 and EP 0 196 194.

The molded or extruded thermoplastic article, optionally, comprises 0 to50 weight percent of a polymeric toughener comprising a reactivefunctional group and/or a metal salt of a carboxylic acid. In oneembodiment the molded or extruded thermoplastic article comprises 2 to20 weight percent polymeric toughener selected from the group consistingof: a copolymer of ethylene, glycidyl(meth)acrylate, and optionally oneor more (meth)acrylate esters; an ethylene/α-olefin orethylene/α-olefin/diene copolymer grafted with an unsaturated carboxylicanhydride; a copolymer of ethylene, 2-isocyanatoethyl(meth)acrylate, andoptionally one or more (meth)acrylate esters; and a copolymer ofethylene and acrylic acid reacted with a Zn, Li, Mg or M_(n) compound toform the corresponding ionomer.

The thermoplastic composition may also comprise other additives commonlyused in the art, such other heat stabilizers or antioxidants referred toas “co-stabilizers”, antistatic agents, blowing agents, lubricants,plasticizers, and colorant and pigments.

Co-stabilizers including copper stabilizers, secondary aryl amines,hindered amine light stabilizers (HALS), hindered phenols, and mixturesthereof, may be used in the compositions of the invention. Preferredco-stabilizers are selected from the group consisting of secondary arylamines, hindered amine light stabilizers (HALS), hindered phenols, andmixtures thereof.

A significant advantage of the thermoplastic compositions is that highthermal stability is provided without the use of conventional copperheat stabilizers. Copper heat stabilizers tend to act as corrosiveagents over long periods of time at elevated temperatures; and in someenvironments actually cause degradation of semiaromatic polymers. Thus,another embodiment is a thermoplastic composition, as disclosed above,having less than 25 ppm copper as determined with atomic absorptionspectroscopy.

Herein the thermoplastic composition is a mixture by melt-blending, inwhich all polymeric ingredients are adequately mixed, and allnon-polymeric ingredients are adequately dispersed in a polymer matrix.Any melt-blending method may be used for mixing polymeric ingredientsand non-polymeric ingredients of the present invention. For example,polymeric ingredients and non-polymeric ingredients may be fed into amelt mixer, such as single screw extruder or twin screw extruder,agitator, single screw or twin screw kneader, or Banbury mixer, and theaddition step may be addition of all ingredients at once or gradualaddition in batches. When the polymeric ingredient and non-polymericingredient are gradually added in batches, a part of the polymericingredients and/or non-polymeric ingredients is first added, and then ismelt-mixed with the remaining polymeric ingredients and non-polymericingredients that are subsequently added, until an adequately mixedcomposition is obtained. If a reinforcing filler presents a longphysical shape (for example, a long glass fiber), drawing extrusionmolding may be used to prepare a reinforced composition.

The thermoplastic composition having a polyhydric alcohol having two ormore hydroxyl groups, as disclosed above, is useful in increasinglong-term thermal stability at high temperatures of molded or extrudedarticles made therefrom. The long-term thermal stability of the articlescan be assessed by air oven ageing of 4 mm thick test samples at varioustest temperatures for various test periods of time. The oven testtemperatures for the composition disclosed herein are a minimum of 210°C. and a minimum of 500 hours test periods. The test temperatures andthe test periods may be higher. The test samples, after air oven ageing,are tested for tensile strength and elongation to break, according toISO 527-2/1A test method; and compared with non-aged controls that aredry as molded (DAM). The comparison with the DAM controls provides theretention of tensile strength and/or retention of elongation to break,and thus the various compositions can be assessed as to long-term hightemperature ageing performance.

In various embodiments of the invention the thermoplastic compositionhave an AOA 210° C./1000 hours retention of tensile strength of at least70% and preferably at least 80, and 85%, based upon comparison with DAMnon-aged controls.

In another aspect, the present invention relates a use of the abovedisclosed thermoplastic compositions for high temperature applications.

In another aspect, the present invention relates to a method formanufacturing an article by shaping the thermoplastic composition of theinvention. Examples of articles are films or laminates, automotive partsor engine parts or electrical/electronics parts. By “shaping”, it ismeant any shaping technique, such as for example extrusion, injectionmoulding, thermoform moulding, compression moulding or blow moulding.Preferably, the article is shaped by injection moulding or blowmoulding. The molded or extruded thermoplastic articles disclosed hereinmay have application in many vehicular components that meet one or moreof the following requirements: high impact requirements; significantweight reduction (over conventional metals, for instance); resistance tohigh temperature; resistance to oil environment; resistance to chemicalagents such as coolants; and noise reduction allowing more compact andintegrated design. Specific molded or extruded thermoplastic articlesare selected from the group consisting of charge air coolers (CAC);cylinder head covers (CHC); oil pans; engine cooling systems, includingthermostat and heater housings and coolant pumps; exhaust systemsincluding mufflers and housings for catalytic converters; air intakemanifolds (AIM); and timing chain belt front covers. As an illustrativeexample of desired mechanical resistance against long-term hightemperature exposure, a charge air cooler can be mentioned. A charge aircooler is a part of the radiator of a vehicle that improves enginecombustion efficiency. Charge air coolers reduce the charge airtemperature and increase the density of the air after compression in theturbocharger thus allowing more air to enter into the cylinders toimprove engine efficiency. Since the temperature of the incoming air canbe more than 200° C. when it enters the charge air cooler, it isrequired that this part be made out of a composition maintaining goodmechanical properties under high temperatures for an extended period oftime.

The present invention is further illustrated by the following examples.It should be understood that the following examples are for illustrationpurposes only, and are not used to limit the present invention thereto.

Materials IN THE EXAMPLES AND COMPARATIVE EXAMPLES

PA66 refers to an aliphatic polyamide made of 1,6-hexanedioic acid and1,6-hexamethylenediamine, commercially available from E.I. DuPont deNemours and Company, Wilmington, Del., USA under the trademark Zytel®101 NC010.

PA6 refers to Ultramid® B27 poly(ε-caprolactam) available from BASF,USA.

DPE refers to dipentaerythritol that was from Perstorp SpecialityChemicals AB, Perstorp, Sweden as Di-Penta 93.

Glass fibers A 4.5 mm length chopped glass fibers, refers to OCV 983,available from Owens Corning Vetrotex, France.

Glass Fiber B refers to PPG 3660 chopped glass fiber available fro PPGIndustries, Pittsburgh, Pa.

Black Pigment A refers to 40 wt % nigrosine black pigment concentrate ina PA66 carrier.

Cu heat stabilizer refers to a mixture of 7 parts of potassium iodideand 1 part of copper iodide in 0.5 part of a stearate wax binder.

Polyamide A refers to PA66/6T (75/25 molar ratio repeat units) withamine ends approximately 50 meq/kg that was provided according to thefollowing procedure: Polyamide 66 salt solution (3928 lbs. of a 51.7percent by weight with a pH of 8.1) and 2926 lbs of a 25.2% by weight ofpolyamide 6T salt solution with a pH of 7.6 were charged into anautoclave with 100 g of a conventional antifoam agent, 20 g of sodiumhypophosphite, 220 g of sodium bicarbonate, 2476 g of 80% HMD solutionin water, and 1584 g of glacial acetic. The solution was then heatedwhile the pressure was allowed to rise to 265 psia at which point, steamwas vented to maintain the pressure at 265 psia and heating wascontinued until the temperature of the batch reached 250° C. Thepressure was then reduced slowly to 6 psia, while the batch temperaturewas allowed to further rise to 280-290° C. The pressure was then held at6 psia and the temperature was held at 280-290° C. for 20 minutes.Finally, the polymer melt was extruded into strands, cooled, and cutinto pellets. The resulting polyamide 66/6T is referred to herein asPolyamide A having a melting point of about 268≡1° C., relativeviscosity (according to ASTM D-789 method) of 42±2; NH2 ends of 43±2meg/kg and COOH ends of 88±5 meg/kg.

Polyamide B, referring to PA66/6T (75/25 molar ratio repeat units) withhigh amine ends (i.e. at least 70 meq/kg), was provided according to thefollowing procedure:

-   Polyamide 66/6T salt solution (214.25 lbs. of a 39.70 percent by    weight) was prepared from hexamethylenediamine, adipic acid, and    terephthalic acid in water, where the molar ratio of 1,6-adipic acid    to terephthalic acid is 75:25. The salt solution had a pH of    8.20±0.05 and was charged into an autoclave with 3.5 g of a 10    percent by weight solution of a conventional antifoam agent in    water, 0.7 g of sodium hypophosphite, 7.7 g of sodium bicarbonate,    237.5 g of 80% HMD solution in water, and 15 g of glacial acetic    acid. The solution was then heated while the pressure was allowed to    rise to 265 psia at which point, steam was vented to maintain the    pressure at 265 psia and heating was continued until the temperature    of the batch reached 255° C. The pressure was then reduced slowly to    10 psia, while the batch temperature was allowed to further rise to    275-285° C. The pressure was then held at 10 psia and the    temperature was held at 275-285° C. for 20 minutes. Finally, the    polymer melt was extruded into strands, cooled, and cut into    pellets. The resulting polyamide 66/6T is referred to herein as    Polyamide B having a melting point of about 269±1° C.; relative    viscosity (according to ASTM D-789 method) of 44±2, NH2 ends of 88±2    meg/kg and COOH ends of 51±5 meg/kg.

Methods

Compounding Method

The compositions of Examples were prepared by melt blending theingredients listed in the Tables in a 40 mm twin screw extruder(Berstorff ZE40) operating at about 280° C. using a screw speed of about300 rpm, a throughput of 110 kg/hour and a melt temperature measured byhand of about 290° C. The glass fibers were added to the melt through ascrew side feeder. Ingredient quantities shown in the Tables are givenin weight percent on the basis of the total weight of the thermoplasticcomposition.

The compounded mixture was extruded in the form of laces or strands,cooled in a water bath, chopped into granules and placed into sealedaluminum lined bags in order to prevent moisture pick up. The coolingand cutting conditions were adjusted to ensure that the materials werekept below 0.15 wt % of moisture level.

Physical Properties Measurement

Mechanical tensile properties, i.e. E-modulus, stress at break (Tensilestrength) and strain at break (elongation at break) were measuredaccording to ISO 527-2/1A. Measurements were made on injection moldedISO tensile bar (melt temperature=295-300° C.; mold temperature=100° C.and a hold pressure of 85 MPa) with a thickness of the test specimen of4 mm and a width of 10 mm according to ISO 527/1A at a testing speed of5 mm/min (tensile strength and elongation) and 50 mm/min forunreinforced samples. Tensile Modulus was measured at 1 mm/min.

Air Oven Ageing (AOA)

The test specimens were heat aged in a re-circulating air ovens (Heraeustype UT6060) according to the procedure detailed in ISO 2578. At variousheat aging times, the test specimens were removed from the oven, allowedto cool to room temperature and sealed into aluminum lined bags untilready for testing. The tensile mechanical properties were then measuredaccording to ISO 527 using a Zwick tensile instrument. The averagevalues obtained from 5 specimens are given in the Tables.

Retention of E-modulus, stress at break and strain at break correspondsto the percentage of the E-modulus, stress at break and strain at breakafter heat aging for 500 hours 1000 hours in comparison with that of anunexposed control of the same composition and shape considered as being100%.

Examples 1 and 2 and Comparative Examples C-1-C-4

Compositions of Examples 1 and 2 and C-1-C-4 are listed in Table 7.Examples 1 and C-3 show the heat ageing performance of PA66/6T (75/25molar ratio) having a number of amine ends of about 45 meq/Kg. Tensileproperties after AOA at 210° C. at 500 h and 1000 h, and tensileproperties of non-heat-aged control; and retention of physicalproperties; are listed in Table 1. The Examples show that the presenceof DPE at 1.5 wt % level provides significant improvement in retentionof tensile strength, and especially at 1000 h and 210° C., as comparedto the comparative examples having the conventional copper stabilizer.Additionally, Example 2 having amine ends of 88±2 meg/kg surprisinglyshows significant improvement in retention of tensile strength, ascompared to Example 1 having NH2 ends of 43±2 meg/kg. Both Examples 1and 2 show significant improvement in retention of tensile strength, ascompared with Comparative Examples C-1 and C-2 containing conventionalPA66.

TABLE 1 Example C-1 C-2 C-3 1 C-4 2 PA66 68.85 67.80 Polyamide A (66/6T)68.85 67.80 Polyamide B (66/6T) 68.85 67.80 Glass Fiber B 30.00 30.0030.00 30.00 30.00 30.00 Black Pigment A 0.70 0.70 0.70 0.70 0.70 0.70 CuHeat stabilizer 0.45 0.45 0.45 DPE 1.50 1.50 1.50 Tensile properties DAMTensile Modulus [MPa] 9747.0 9811.0 8791.0 8848.0 9207.7 8631.0 TensileStrength [MPa] 207.8 205.2 198.6 189.1 196.1 187.2 Elongation @ Break[%] 3.8 3.4 3.7 3.2 5.5 3.4 Tensile properties 500 h at 210° C. TensileModulus [MPa] 9558.0 9028.0 8353.0 8549.0 8377.0 8355.0 Tensile Strength[MPa] 160.7 210.0 148.0 198.5 151.3 202.0 Retention Tensile 77.3% 102.3%74.5% 105.0% 77.1% 107.9% Strength [%] Elongation @ Break [%] 2.0 3.31.9 3.4 2.0 3.8 Tensile properties 1000 h at 210° C. Tensile Modulus[MPa] 7353 9700 9142 9392 9404 9310 Tensile Strength [MPa] 62.0 127.086.0 152.0 101.0 165 Retention Tensile 29.8% 61.9% 43.3% 80.4% 51.5%88.1% Strength [%] Elongation @ Break [%] 1.1 1.8 1.1 2.1 1.2 2.4

Example 3

This Example illustrates the unexpected and surprising results providedby a blend of Group (II) polyamide (PA6) with Group (III) polyamide(PA66/6T) having high amine ends (88 meq/Kg). Example 3, listed in Table2, contains PA66/6T and 5 wt % PA6, and has a 98.6% retention of tensilestrength after AOA at 1000 h and 210° C., compared with Example 2containing PA66/6T alone, which shows 88.1% retention of tensilestrength under the same conditions. This indicates that blends ofpolyamides can have significantly improved properties over that of thebase polyamide comprising the major fraction of the blend.

TABLE 8 Example 14 Polyamide B (66/6T) 57.81 PA6 5.00 Glass Fiber A35.00 Black Pigment A 0.69 DPE 1.50 Tensile properties DAM TensileModulus [MPa] 11300 Tensile Strength [MPa] 208 Elongation @ Break [%]3.4 Tensile properties 500 h at 210° C. Tensile Modulus [MPa] 11425Tensile Strength [MPa] 227 Retention Tensile Strength (%) 109.1Elongation @ Break [%] 3.5 Tensile properties 1000 h at 210° C. TensileModulus [MPa] 11418 Tensile Strength [MPa] 205 Retention TensileStrength (%) 98.6 Elongation @ Break [%] 2.7

1. A thermoplastic composition comprising A) a polyamide resincomprising one or more polyamides selected from the group consisting ofGroup (III) Polyamides comprising (a) about 20 to about 35 mole percentsemiaromatic repeat units derived from monomers selected from one ormore of the group consisting of: i) aromatic dicarboxylic acids having 8to 20 carbon atoms and aliphatic diamines having 4 to 20 carbon atoms;and (b) about 65 to about 80 mole percent aliphatic repeat units derivedfrom monomers selected from one or more of the group consisting of: ii)an aliphatic dicarboxylic acid having 6 to 20 carbon atoms and saidaliphatic diamine having 4 to 20 carbon atoms; iii) a lactam and/oraminocarboxylic acid having 4 to 20 carbon atoms; B) about 0.25 to about15 weight percent of one or more polyhydric alcohols having more thantwo hydroxyl groups and a having a number average molecular weight(M_(n)) of less than 2000, the weight percentage being based on thetotal weight of said thermoplastic composition; and C) 0 to 60 weightpercent of one or more reinforcement agents.
 2. The thermoplasticcomposition of claim 1 wherein said polyamide resin has at least about60 meq/Kg of amine ends.
 3. The thermoplastic composition of claim 1wherein said polyamide resin has at least about 70 meq/Kg of amine ends.4. The thermoplastic composition of claim 1 wherein said polyamide resincomprises one or more polyamides having a melting point of at least 210°C. and selected from the group consisting of poly(tetramethylenehexanediamide/tetramethylene terephthalamide) (PA46/4T),poly(tetramethylene hexanediamide/hexamethylene terephthalamide)(PA46/6T), poly(tetramethylene hexanediamide/2-methylpentamethylenehexanediamide/decamethylene terephthalamide) PA46/D6/10T),poly(hexamethylene hexanediamide/hexamethylene terephthalamide)(PA66/6T), poly(hexamethylene hexanediamide/hexamethyleneisophthalamide/hexamethylene terephthalamide PA66/6I/6T, andpoly(hexamethylene hexanediamide/2-methylpentamethylenehexanediamide/hexamethylene terephthalamide (PA66/D6/6T).
 5. Thethermoplastic composition of claim 1 wherein polyamide resin has amelting point of at least of 260° C. as determined with differentialscanning calorimetry at 10° C./min scan rate in the first heating scan.6. The thermoplastic composition of claim 5 wherein said semiaromaticrepeat unit is derived from terephthalic acid.
 7. The thermoplasticcomposition of claim 6 wherein said aliphatic repeat unit is derivedfrom adipic acid.
 8. The thermoplastic composition of claim 6 or 7wherein said aliphatic diamine is 1,4-butane diamine or1,6-hexanediamine.
 9. The thermoplastic composition of claim 1 furthercomprising (D) 0.1 to 30 weight percent of one or more blendingpolyamide(s) independently selected from the group consisting of Group(I) Polyamides having a melting point of less than 210° C., andcomprising an aliphatic or semiaromatic polyamide selected from thegroup poly(pentamethylene decanediamide) (PA510), poly(pentamethylenedodecanediamide) (PA512), poly(ε-caprolactam/hexamethylenehexanediamide) (PA6/66), poly(ε-caprolactam/hexamethylene decanediamide)(PA6/610), poly(ε-caprolactam/hexamethylene dodecanediamide) (PA6/612),poly(hexamethylene tridecanediamide) (PA613), poly(hexamethylenepentadecanediamide) (PA615), poly(ε-caprolactam/tetramethyleneterephthalamide) (PA6/4T), poly(ε-caprolactam/hexamethyleneterephthalamide) (PA6/6T), poly(ε-caprolactam/decamethyleneterephthalamide) (PA6/10T), poly(ε-caprolactam/dodecamethyleneterephthalamide) (PA6/12T), poly(hexamethylenedecanediamide/hexamethylene terephthalamide) (PA610/6T),poly(hexamethylene dodecanediamide/hexamethylene terephthalamide)(PA612/6T), poly(hexamethylene tetradecanediamide/hexamethyleneterephthalamide) (PA614/6T), poly(ε-caprolactam/hexamethyleneisophthalamide/hexamethylene terephthalamide) (PA6/61/6T),poly(ε-caprolactam/hexamethylene hexanediamide/hexamethylenedecanediamide) (PA61661610), poly(ε-caprolactam/hexamethylenehexanediamide/hexamethylene dodecanediamide) (PA61661612),poly(ε-caprolactam/hexamethylene hexanediamide/hexamethylenedecanediamide/hexamethylene dodecanediamide) (PA6/66/610/612),poly(2-methylpentamethylene hexanediamide/hexamethylenehexanediamide/hexamethylene terephthamide) (PA D6166//6T),poly(2-methylpentamethylene hexanediamide/hexamethylene hexanediamide/)(PA D6/66), poly(decamethylene decanediamide) (PA1010),poly(decamethylene dodecanediamide) (PA1012), poly(decamethylenedecanediamide/decamethylene terephthalamide) (PA1010/10T)poly(decamethylene decanediamide/dodecamethylenedecanediamide/decamethylene terephthalamide/dodecamethyleneterephthalamide (PA1010/1210/10T/12T), poly(11-aminoundecanamide)(PA11), poly(11-aminoundecanamide/tetramethylene terephthalamide)(PA11/4T), poly(11-aminoundecanamide/hexamethylene terephthalamide)(PA11/6T), poly(11-aminoundecanamide/decamethylene terephthalamide)(PA11/10T), poly(11-aminoundecanamide/dodecamethylene terephthalamide)(PA11/12T), poly(12-aminododecanamide) (PA12),poly(12-aminododecanamide/tetramethylene terephthalamide) (PA12/4T),poly(12-aminododecanamide/hexamethylene terephthalamide) (PA12/6T),poly(12-aminododecanamide/decamethylene terephthalamide) (PA12/10T)poly(dodecamethylene dodecanediamide) (PA1212), and poly(dodecamethylenedodecanediamide/dodecamethylene dodecanediamide/dodecamethyleneterephthalamide)) (PA1212/12T); and Group (II) Polyamides having amelting point of at least 210° C., and comprising an aliphatic polyamideselected from the group consisting of poly(tetramethylene hexanediamide)(PA46), poly(ε-caprolactam) (PA 6), poly(hexamethylenehexanediamide/(ε-caprolactam/) (PA 66/6) poly(hexamethylenehexanediamide) (PA 66), poly(hexamethylene hexanediamide/hexamethylenedecanediamide) (PA66/610), poly(hexamethylenehexanediamide/hexamethylene dodecanediamide) (PA66/612),poly(hexamethylene hexanediamide/decamethylene decanediamide) (PA66/1010), poly(hexamethylene decanediamide) (PA610), poly(hexamethylenedodecanediamide) (PA612), poly(hexamethylene tetradecanediamide)(PA614), poly(hexamethylene hexadecanediamide) (PA616), andpoly(tetramethylene hexanediamide/2-methylpentamethylene hexanediamide)(PA46/D6).
 10. The thermoplastic composition of claim 9 wherein the oneor more blending polyamide(s) is selected from Group (I) Polyamides. 11.The thermoplastic composition of claim 9 wherein the one or moreblending polyamide(s) is selected from Group (II) Polyamides.
 12. Thethermoplastic composition of claim 11 wherein the one or more blendingpolyamide(s) is selected from poly(ε-caprolactam) (PA 6) andpoly(hexamethylene hexanediamide) (PA 66).
 13. The thermoplasticcomposition of claim 1 wherein said one or more polyhydric alcohols isselected from the group selected from tripentaerythritol,dipentaerythritol and/or pentaerythritol.
 14. The thermoplasticcomposition of claim 1 wherein the resin composition comprise one ormore reinforcement agents selected from the group consisting calciumcarbonate, glass fibers with circular and noncircular cross-section,glass flakes, glass beads, carbon fibers, talc, mica, wollastonite,calcined clay, kaolin, diatomite, magnesium sulfate, magnesium silicate,barium sulfate, titanium dioxide, sodium aluminum carbonate, bariumferrite, potassium titanate and mixtures thereof.
 15. The thermoplasticcomposition of claim 1 wherein said polyamide composition comprises lessthan 25 ppm copper as determined with atomic absorption spectroscopy.